This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2000-299852, filed Sep. 29, 2000, the entire contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a proton conductive film for an electrolytic membrane for a fuel cell and a fuel cell using the particular proton conductive film.
2. Description of the Related Art
Conventional methanol fuel cells are classified according to the feed method of the liquid fuel, into a liquid feed type and a gasified fuel supply type. In the fuel cell of the gasified fuel feed type, the electrode reaction is carried out between the electrode and the gasified fuel. As a result, it is possible to obtain a high performance with a high reactivity. On the other hand, the system is made highly complex, making it difficult to miniaturize the system.
When it comes to the fuel cell of a liquid feed type, the system is rendered relatively simple, compared with the gasified fuel feed type. However, since the electrode reaction is carried out between the electrode and the liquid fuel, the reactivity is low, leading to the problem of a low performance. The liquid fuel cell utilizing capillary force for fuel supply is also of the liquid feed type in which the fuel is supplied in a liquid state to the fuel electrode and, thus, does not require a pump or the like. Therefore, the liquid fuel cell of this type is also adaptable for miniaturization. However, the activity of the electrode reaction is low and, thus, is low in its performance.
In addition to the problems described above, the greatest problem inherent in the fuel cell is that, where a proton conductive solid polymer film such as a film of perfluorosulfonic acid available under the trade name of xe2x80x9cNafionxe2x80x9d from Du Pont Inc., USA, is used as an electrolytic membrane, generated is the cross-over problem caused by the permeation of an organic liquid fuel such as methanol through the electrolytic membrane to reach the electrode of the oxidizing agent. Where the cross-over phenomenon has taken place, the supplied liquid fuel reacts directly with the oxidizing agent, resulting in failure to output the energy as the electric power. It follows that a decisive problem is generated that it is impossible to obtain a stable output.
As described above, in the conventional fuel cell, the proton conductive solid polymer film was incapable of sufficiently suppressing the cross-over of methanol, resulting in failure to supply a stable output.
The present invention, which has been achieved in view of the situation described above, is intended to provide a proton conductive film capable of suppressing the cross-over of methanol while maintaining the proton conductivity.
The present invention is also intended to provide a fuel cell supplying a stable output.
According to a one aspect of the present invention, there is provided a proton conductive film for an electrolytic membrane for a fuel cell, the proton conductive film being a composite body comprising a proton conductive polymer and a polymer represented by general formula (1) given below: 
where, X represents a functional group having a nitrogen atom, A represents a substituted or unsubstituted divalent organic group, and n is an integer.
According to another aspect of the present invention, there is provided a proton conductive film for an electrolytic membrane for a fuel cell, the proton conductive film being a composite body comprising a proton conductive polymer, and a copolymer between a polymer represented by general formula (1) given below, and a metal oxide represented by general formula (2) given below: 
where, X represents a functional group having a nitrogen atom, A represents a substituted or unsubstituted divalent organic group, n is an integer, M is a metal selected from the group consisting of Ti, Zr, Al, B, Mo, W, Ru, Ir, Ge, Si and V, x is 1 or 2, and y is 2, 3, 4 or 5.
According to another aspect of the present invention, there is provided a fuel cell, comprising an electrolytic membrane including a proton conductive film, which is a composite body comprising a proton conductive polymer and a polymer represented by general formula (1) given below: 
where, X represents a functional group having a nitrogen atom, A represents a substituted or unsubstituted divalent organic group, and n is an integer; and
a fuel electrode and an oxidizing agent electrode arranged to have the electrolytic membrane sandwiched there between.
Further, according to another aspect of the present invention, there is provided a fuel cell comprising an electrolytic membrane including a proton conductive film, which is a composite body comprising a proton conductive polymer, and a copolymer between a polymer represented by general formula (1) given below, and a metal oxide represented by general formula (2) given below: 
where, X represents a functional group having a nitrogen atom, A represents a substituted or unsubstituted divalent organic group, n is an integer, M is a metal selected from the group consisting of Ti, Zr, Al, B, Mo, W, Ru, Ir, Ge, Si and V, x is 1 or 2, and y is 2, 3, 4 or 5; and
a fuel electrode and an oxidizing agent electrode arranged to have the electrolyte membrane sandwiched there between.